A kind of α-AlH3 and preparation method

Abstract

The present invention discloses an α-AlH 3 and preparation method, LiAlH 4 and AlCl 3 AlH was prepared by mixed reaction 3 ether, AlH 3 The ether compound is added to the confined solvent to react to obtain α-AlH 3 The confined solvent includes any one of toluene and N-methylpyrrolidone, silicone, and diphenyl ether. The confined solvent used in the present invention is AlH 3 The ether compound is easy to deetherify and crystallize, and the used solvent can be recycled, and the whole operation process is simple and feasible. The prepared product has high thermal stability.

Description

Technical Field

[0001] The present invention relates to the field of propellant material preparation, and in particular to α-AlH3 and a preparation method thereof. Background Art

[0002] α-AlH3 is a binary covalent hydride with a mass hydrogen storage of up to 10.08% and a volume hydrogen storage of 0.148 Kg / L (twice the density of liquid hydrogen). Given its high hydrogen content, high combustion heat, and non-toxicity, it can be used in the field of high-energy fuels. Calculations show that replacing aluminum with AlH3 can produce lower flame temperatures and higher gas production, and can provide a higher specific impulse than aluminum fuel. At the same time, since AlH3 is composed of two strongly reducing atoms, H2 is produced during its combustion process, and H2 can promote the rapid combustion of the oxidant to generate Al2O3 and H2O and release a large amount of heat energy. Therefore, AlH3 has the potential to become a new type of high-energy additive due to its advantages such as high combustion heat, good gas formation, and non-toxicity.

[0003] α-AlH3 is the most thermodynamically stable of the seven AlH3 crystal forms (α, α′, β, γ, ε, δ, ξ), and is also the only crystal form with application prospects in propellant formulations. There are many methods for preparing α-AlH3, mainly based on the traditional ether method. The current traditional ether method has a large reaction system, complex and cumbersome operating procedures, and a large amount of toxic and harmful waste solvents produced during the preparation process, which also poses a threat to human health. In addition, the prepared product has poor thermal stability and is easy to decompose. This problem seriously restricts its application in high-energy propellants. Therefore, it is particularly important to study a method for preparing α-AlH3 that is simple to operate, easy to control reaction conditions, and has high thermal stability. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects of the prior art and provide an α-AlH3 and a preparation method thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing α-AlH3 comprises: preparing AlH3 etherate by a mixed reaction of LiAlH4 and AlCl3, adding the AlH3 etherate into a confined solvent to react and obtain α-AlH3, wherein the confined solvent comprises one or more of N-methylpyrrolidone, silicone, diphenyl ether and toluene.

[0007] Furthermore, the mass ratio of LiAlH4 to anhydrous AlCl3 is (3-5): (2-4).

[0008] Furthermore, the mass ratio of the AlH3 etherate to the confined solvent is (1-10): (100-500).

[0009] Furthermore, the volume ratio of any one of the N-methylpyrrolidone, silicone, and diphenyl ether to toluene is (1-2):20

[0010] Specifically, the steps include:

[0011] Step 1: Add LiAlH4 into the reaction flask under N2 protection and cool to below 0°C in an ice-salt bath;

[0012] Step 2: Add anhydrous AlCl3 into another reaction bottle, and then add anhydrous ether to dissolve it;

[0013] Step 3: under N2 protection, the solution of step 2 is added dropwise to the reaction bottle of step 1, and after the addition is completed, the reaction is continued, and then the obtained AlH3 etherate solution is filtered;

[0014] Step 4: Under the protection of N2, add the AlH3 etherate solution obtained in step 3 into the confined solvent, heat it up and then keep it warm. After the reaction is completed, naturally cool it to room temperature and filter it to obtain α-AlH3.

[0015] Wherein, the confined solvent includes any one of toluene, N-methylpyrrolidone, silicone and diphenyl ether.

[0016] Furthermore, in step 2, the ratio of anhydrous AlCl3 to anhydrous ether is (1-10) g: (10-200) mL.

[0017] Furthermore, the reaction time of step 3 is 10 to 30 minutes.

[0018] Furthermore, in step 4, the heating temperature is 80-100° C. and the temperature is kept for 1-2 hours.

[0019] An α-AlH3 prepared by the preparation method of α-AlH3 of the present invention, wherein the single grain size of the α-AlH3 is 1.8-2.2 μm, and the thermal decomposition temperature of the α-AlH3 is 191.3°C.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] Compared with the existing solvents, the limited domain solvent used in the present invention is easy to deetherify and crystallize AlH3 etherate, thus overcoming the defects of the products obtained in the prior art, such as many defects, easy decomposition, and poor crystal density. The products prepared by using the limited domain solvent have high thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1XRD spectrum of the sample α-AlH3 prepared by the present invention;

[0023] Figure 2 SEM spectrum of the sample α-AlH3 prepared by the present invention;

[0024] Figure 3 DSC spectrum of the sample α-AlH3 prepared by the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with embodiments, the purpose of which is to provide a better understanding of the essential features of the present invention as embodied in the contents of the present invention. Therefore, the examples given should not be regarded as limiting the scope of protection of the present invention.

[0026] The limited solvent of the present invention refers to a solvent that can make the AlH3 ether compound easy to deetherify and crystallize in a certain area, and the crystallization process is controllable. It includes any one of toluene and N-methylpyrrolidone, silicone, and diphenyl ether.

[0027] The principle of the present invention is that under the action of the confined solvent, the deetherification crystallization process of the ether compound is controllable, the generated crystals have high density and fewer defects, so the thermal stability of the crystals is high.

[0028] The preparation method of the present invention specifically comprises the following steps:

[0029] Step 1: Add LiAlH4 into the reaction bottle under N2 protection and cool to below 0℃ in an ice-salt bath;

[0030] Step 2: Add anhydrous AlCl3 into another reaction bottle, and then add anhydrous ether to dissolve it;

[0031] Step 3: under N2 protection, the solution of step 2 is added dropwise to the reaction bottle of step 1 for reaction, and then the obtained AlH3 etherate solution is filtered;

[0032] Step 4: Under the protection of N2, add the AlH3 etherate solution obtained in step 3 into the confined solvent, heat it up and then keep it warm. After the reaction is completed, naturally cool it to room temperature and filter it to obtain α-AlH3.

[0033] The confined solvent includes toluene and any one of N-methylpyrrolidone, silicone, and diphenyl ether, wherein the volume ratio of any one of N-methylpyrrolidone, silicone, and diphenyl ether to toluene is (1-2):20.

[0034] In step 2, the ratio of anhydrous AlCl3 to anhydrous ether is (1~10) g: (10~200) mL.

[0035] The sample structure and phase composition of the present invention were determined by X-ray diffraction (XRD) analysis using a Japanese Rigaku D / MAX-2400 X-ray powder diffractometer with an X-ray source of Cu K α, wavelength 1.54056Å, tube voltage 40KV, tube current 80 mA, scanning range 2 θ =3°~90°, step size 0.02°.

[0036] Example 1

[0037] This embodiment provides a method for preparing α-AlH3, wherein the confined solvent is a mixture of N-methylpyrrolidone and toluene, and comprises the following steps:

[0038] Step 1: Add 4.0 g LiAlH4 into the reaction flask under N2 protection and cool to below 0 °C in an ice-salt bath;

[0039] Step 2: Add 3.6 g of anhydrous AlCl3 into another reaction bottle, and then add 50 mL of anhydrous ether to dissolve it;

[0040] Step 3: under N2 protection, the solution of step 2 was added dropwise to the reaction bottle of step 1, and the reaction was continued for 30 min after the addition was completed, and then the obtained AlH3 etherate solution was filtered;

[0041] Step 4: Under N2 protection, add the AlH3 etherate solution obtained in step 3 to a mixture of 300 mL of N-methylpyrrolidone and toluene, with a volume ratio of N-methylpyrrolidone to toluene of 1:20, heat to 100 °C, keep warm for 1 h, and naturally cool to room temperature after the reaction is completed. Filter to obtain α-AlH3.

[0042] Example 2

[0043] This embodiment is the same as Embodiment 1, except that the confined solvent is a mixture of diphenyl ether and toluene.

[0044] Step 1: Add 3.6 g LiAlH4 into the reaction flask under N2 protection and cool to below 0 °C in an ice-salt bath;

[0045] Step 2: Add 3.3 g of anhydrous AlCl3 into another reaction bottle, and then add 50 mL of anhydrous ether to dissolve it;

[0046] Step 3: under N2 protection, the solution of step 2 was added dropwise to the reaction bottle of step 1, and the reaction was continued for 30 min after the addition was completed, and then the obtained AlH3 etherate solution was filtered;

[0047] Step 4: Under N2 protection, add a confined solvent to the AlH3 ether solution obtained above: 500 mL of a mixture of diphenyl ether and toluene, with a volume ratio of diphenyl ether to toluene of 1.5:20, heat to 90 °C, keep warm for 2 h, and naturally cool to room temperature after the reaction is completed. Filter to obtain α-AlH3 with high thermal stability.

[0048] Example 3

[0049] This embodiment is the same as Embodiment 1, except that the confined solvent is a mixture of silicone and toluene.

[0050] Step 1: Add 3.2 g LiAlH4 into the reaction bottle under N2 protection and cool to below 0 °C in an ice-salt bath;

[0051] Step 2: Add 2.9 g of anhydrous AlCl3 into another reaction bottle, and then add 50 mL of anhydrous ether to dissolve it;

[0052] Step 3: under N2 protection, the solution of step 2 was added dropwise to the reaction bottle of step 1, and the reaction was continued for 30 min after the addition was completed, and then the obtained AlH3 etherate solution was filtered;

[0053] Step 4: Under N2 protection, add a confined solvent to the AlH3 etherate solution obtained above: 500 mL of a mixture of silicone and toluene, with a volume ratio of silicone to toluene of 2:20, heat to 80 °C, keep warm for 1.5 h, and naturally cool to room temperature after the reaction is completed. Filter to obtain α-AlH3 with high thermal stability.

[0054] Figure 1 The XRD pattern of the sample prepared for the invention is compared with the standard XRD pattern of α-AlH3. θ Characteristic diffraction peaks of α-AlH3 appeared at 27.70°, 38.55°, 40.54°, 46.11°, 49.76°, 57.06°, 63.00°, 66.01°, 67.96°, 72.24°, 73.74°, 82.51°, 86.03°, and 87.50, and no other impurity peaks appeared.

[0055] pass Figure 2 SEM test shows that the morphology of α-AlH3 is small cubes gathered into spherical clusters, the single grain size is small, about 2μm, and the surface is smooth and defect-free. The crystal density is high.

[0056] Figure 3The DSC test shows that the thermal decomposition temperature of the product prepared by the present invention is 191.3°C, which is about 8°C higher than the thermal decomposition temperature of the product prepared without using a confined solvent, indicating that the thermal stability of the product prepared by the present invention is greatly improved.

[0057] Comparative Example 1

[0058] The difference between this embodiment and embodiment 1 is that the confined solvent is a mixture of cyclohexane and toluene.

[0059] Step 1: Add 1.6 g LiAlH4 into the reaction bottle under N2 protection and cool to below 0°C in an ice-salt bath;

[0060] Step 2: Add 1.45 g of anhydrous AlCl3 into another reaction bottle, and then add 30 mL of anhydrous ether to dissolve it;

[0061] Step 3: under N2 protection, the solution of step 2 was added dropwise to the reaction bottle of step 1, and the reaction was continued for 30 min after the addition was completed, and then the obtained AlH3 etherate solution was filtered;

[0062] Step 4: Under N2 protection, add a confined solvent to the AlH3 etherate solution obtained above: 500 mL of a mixture of cyclohexane and toluene, the volume ratio of cyclohexane to toluene is 1:20, heat to 80°C, keep warm for 1.5 h, naturally cool to room temperature after the reaction is completed, filter, and obtain α-AlH3 with a thermal decomposition temperature of 178°C, which is lower than the thermal stability obtained in the embodiment of the present invention.

[0063] Comparative Example 2

[0064] The difference between this embodiment and embodiment 1 is that the confined solvent is a mixture of cyclopentane and benzene.

[0065] Step 1: Add 3.2 g LiAlH4 into the reaction bottle under N2 protection and cool to below 0 °C in an ice-salt bath;

[0066] Step 2: Add 2.9 g of anhydrous AlCl3 into another reaction bottle, and then add 50 mL of anhydrous ether to dissolve it;

[0067] Step 3: under N2 protection, the solution of step 2 was added dropwise to the reaction bottle of step 1, and the reaction was continued for 30 min after the addition was completed, and then the obtained AlH3 etherate solution was filtered;

[0068] Step 4: Under N2 protection, add a confined solvent to the AlH3 etherate solution obtained above: 500 mL of a mixture of cyclopentane and benzene, the volume ratio of cyclopentane to benzene is 1.5:20, heat to 80°C, keep warm for 1.5 h, naturally cool to room temperature after the reaction is completed, filter, and obtain hot α-AlH3 with a thermal decomposition temperature of 183°C, which is lower than the thermal stability of α-AlH3 prepared in the embodiment of the present invention.

[0069] It can be seen from the examples and comparative examples that the limited domain solvents used in the examples are compared with existing solvents: AlH3 etherate is easy to deetherify and crystallize, which overcomes the problems of many defects of products obtained from existing solvents, easy decomposition, and poor crystal density. The products prepared by using limited domain solvents have high thermal stability. The α-AlH3 obtained in Comparative Examples 1 and 2 has an irregular morphology, a rough and defective surface, and low crystal density. The limited domain solvents used in the present invention make AlH3 etherate easy to deetherify and crystallize, and the solvents used can be recycled, and the entire operation process is simple and feasible. The prepared product has high thermal stability.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing α-AlH3, characterized in that: LiAlH4 and AlCl3 are mixed and reacted to obtain AlH3 etherate, and the AlH3 etherate is added into a confined solvent to react to obtain α-AlH3; The mass ratio of LiAlH4 to AlCl3 is (3-5): (2-4); The confined solvent is a mixture of N-methylpyrrolidone and toluene, and the volume ratio of N-methylpyrrolidone to toluene is 1:20; or the confined solvent is a mixture of diphenyl ether and toluene, and the volume ratio of diphenyl ether to toluene is 1.5:20; or the confined solvent is a mixture of silicone and toluene, and the volume ratio of silicone to toluene is 2:20; The mass ratio of the AlH3 etherate to the confined solvent is (1-10): (100-500); The preparation method of α-AlH3 specifically comprises the following steps: Step 1: Add LiAlH4 into the reaction bottle under N2 protection and cool to below 0℃ in an ice-salt bath; Step 2: Add anhydrous AlCl3 into another reaction bottle, and then add anhydrous ether to dissolve it; the ratio of anhydrous AlCl3 to anhydrous ether in step 2 is (1-10) g: (10-200) mL; Step 3: under N2 protection, the solution of step 2 is added dropwise to the reaction bottle of step 1 for reaction, and then the obtained AlH3 etherate solution is filtered; the reaction time of step 3 is 10 to 30 minutes; Step 4: Under N2 protection, add the AlH3 etherate solution obtained in step 3 to the confined solvent, heat up and then keep warm, naturally cool to room temperature after the reaction is completed, filter, and obtain α-AlH3; the heating temperature in step 4 is 80-100°C, and the temperature is kept for 1-2h.

2. An α-AlH3 prepared by the preparation method of α-AlH3 according to claim 1, characterized in that: The single grain size of the α-AlH3 is 1.8-2.2 μm, and the thermal decomposition temperature of the α-AlH3 is 191.3°C.

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